Have a look at thedevice/switch at the emergency exit doors. It may be that a circuit was closed (meaning current could flow) when the door was closed, so simply unplugging the wires would leave the circuit open. You may need to jumper or otherwise connect two sets of wires. If there is a single wire for the switch, the switch may have made a connection to ground, so it may be a matter of grounding the wire. Basically what Rich said. Please use all safety precautions when testing these theories.